Combined 3D Services
Urethane Casting: The Best-Kept Secret in Low-Volume Manufacturing
By Mike Moussa, PE — Urethane casting is the process most inventors and startups don’t know about. It fills the gap between 3D printing and injection molding, and it can save you thousands.
What Is Urethane Casting?
Urethane casting (also called polyurethane casting or vacuum casting) uses silicone molds to produce parts from liquid polyurethane resins. The result: parts that look, feel, and perform like injection-molded plastic — at a fraction of the tooling cost.
The Process
- Create a master pattern — usually 3D printed (SLA for best surface finish) or CNC machined
- Build a silicone mold — liquid silicone is poured around the master, cured, and cut open to remove the master
- Cast parts — liquid polyurethane is poured or injected into the silicone mold, cured, and demolded
- Repeat — each silicone mold produces 15-25 parts before wearing out
Why It’s the Best-Kept Secret
Looks and Feels Like Injection Molding
Urethane resins can simulate virtually any thermoplastic — ABS, polypropylene, nylon, rubber, clear PC. The surface finish is smooth and professional. Most people can’t tell a urethane cast part from an injection molded one.
Fraction of the Tooling Cost
An injection mold costs $3,000-$30,000. A silicone mold costs $200-$1,500. That’s the game-changer for low-volume production.
Fast
From master pattern to first cast parts: 5-10 business days. An injection mold takes 4-8 weeks.
When to Use Urethane Casting
- 10-200 units — too many for 3D printing (cost), too few for injection molding (tooling)
- Market testing — produce 50 units to sell before investing in injection mold tooling
- Bridge production — sell cast parts while injection molds are being built
- Investor samples — production-quality parts for fundraising without production tooling
- Multiple color/material variations — test different options without retooling
Cost Comparison
| Quantity | 3D Printing | Urethane Casting | Injection Molding |
|---|---|---|---|
| 1 part | $25 | $800+ | $5,000+ |
| 10 parts | $200 | $120/ea | $500+/ea |
| 50 parts | $750 | $60/ea | $105/ea |
| 200 parts | $2,500 | $45/ea | $30/ea |
| 1,000 parts | $10,000 | $40/ea | $7/ea |
Urethane casting hits the sweet spot at 10-200 units. Below that, 3D print. Above that, injection mold.
Materials Available
- Rigid plastics — simulating ABS, polycarbonate, acetal, nylon
- Flexible materials — Shore 20A to 90A (rubber-like to semi-rigid)
- Clear materials — optically clear, simulating polycarbonate or acrylic
- High-temperature — resins rated to 300°F+
- Filled materials — glass-filled for added stiffness, flame-retardant options
Limitations
- Silicone molds wear out after 15-25 parts (new molds can be made from the same master)
- Not suitable for thousands of parts — injection molding takes over at high volumes
- Material properties aren’t identical to production thermoplastics (close, but not exact)
- Thin walls (<1mm) can be challenging
Get Started
If you need 10-200 production-quality plastic parts without $10,000+ in tooling, urethane casting is probably your answer. Send us your CAD file or 3D model and we’ll quote the mold and first run of parts.
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